The present invention generally relates to ring or drum brakes, i.e. brakes in which the rotating element to be braked is an annular drum or ring having axially-extending surfaces, the brake shoes being applied against the internal surfaces of the drum (drum brake) or against both the internal and external surfaces of the drum (ring brake).
Such brakes are most commonly utilised in motor vehicles.
The rotating element is usually carried by a transverse wheel disc by means of which it is adapted to be fixed to the shaft of the wheel to be braked, and the space delimited by the element and this wheel disc is normally open to the outside.
In order to limit the access to this space of contaminants such as road dirt which are capable of impairing the proper operation of the brake, or to prevent access of more damaging contaminants such as loose chippings, it has already been proposed to equip drum brakes, that is to say brakes in which the braking surface is formed only on the inner surface of the rotating braking element, with a protective shield which extends opposite the face of at least a part of this rotating element.
Such a shield is described for example in French Pat. No. 1,524,263 (U.S. Pat. No. 3,481,433), U.S. Pat. No. 2,284,357 and French Pat. Nos. 2,172,516 (U.S. Pat. No. 3,853,207) and 1,524,137 (U.S. Pat. No. 3,481,433).
In French Pat. No. 1,524,263, the protective shield forms a plate and more precisely a closing wall which extends over the whole of the rotating drum-like element.
This affects the normal ventilation of the internal space in the brake, and contaminants entering this space, for example when the vehicle concerned is traversing muddy terrain, can only escape from it with difficulty.
Similar observations can be made with regard to the shields disclosed in U.S. Pat. No. 2,284,357 and French Pat. Nos. 1,524,137 and 2,172,516, even if the protective plate of these devices presents a portion which, spaced away from the general level of the plate, projects into the internal space defined by the rotating element, the protection devices described therein essentially constitute closing walls designed to prevent the ingress of all contaminants into the internal space, to the prejudice of the ventilation of the latter.
The primary object of the present invention is to provide a protective shield for ring or drum brakes which is free from the above disadvantages and which in addition presents other advantages.
A further object of the invention is to provide a ring or drum brake which is fitted with such a protective shield.